Apparatus and method for producing woodfuel briquettes, pellets, compounds, agglomerates, granulates, and the like

ABSTRACT

An apparatus and a method for producing woodfuel briquettes, pellets, compounds, composites, agglomerates, or granulates as source material for subsequent processing in injection molding or extrusion processes, includes a pressing screw with screw spirals, which rotate around a longitudinal axis and which are arranged inside a screw shell. The feed material is conveyed to the pressing screw via a feed chute located at an input side. At the end of the pressing screw, processing tools are arranged, to which the feed material is conveyed by the rotating screw spirals. In the area of the processing tools, the residual moisture in the feed material evaporates due to the heat generated during the processing procedure, and is vented as a steam flow from the apparatus through the screw shell. In order to prevent the steam flow from carrying away part of the feed material, the apparatus includes an expansion chamber, through which the escaping steam flow is channeled, and the flow-through cross section of which is such that it causes the steam flow to decelerate. As a result of the deceleration of the steam flow in the expansion chamber, the particles of the feed material that were carried off by the steam flow can be returned to the feed material.

This nonprovisional application claims priority under 35 U.S.C. § 119(a)on German Patent Application No. DE 102004035260, which was filed inGermany on Jul. 21, 2004, and which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus and a method for producingwoodfuel briquettes, pellets, compounds, composites, agglomerates, orgranulates.

2. Description of the Background Art

Feed material for the production of woodfuel briquettes, pellets,compounds, composites, agglomerates, or granulates, is most often offree-flowing consistency. The feed material is typically conveyed toprocessing tools by a pressing screw, where it is processed inaccordance with its intended use.

To produce simple products, for example, woodfuel briquettes or pellets,it is sufficient to compress the feed material, for example, wood (sawdust, wood fiber, wood chips), and to subsequently press it through amolding tool. The qualitative expectations from such a product arethereby relatively low. The production of high-quality granulates andagglomerates from homogeneous feed material, for example, PE granulate,requires higher constructive expenditures. After compressing, the dryfeed material is thereby conveyed to an agglomerator or an extruder.

In this context, the production of composite materials, primarily ofthermoplastic synthetics and wood, which are marketed, for example, aswindow frames, and construction and furniture parts, is an area that isbecoming increasingly important. The production of these compositematerials is most often done in a two-step procedure, whereby in a firststep, the various components, for example, wood (saw dust, wood fiber,wood chips), synthetics and bonding agents, are mixed together and fedinto an agglomerator, hot mixer, or extruder. The granulates,agglomerates, compounds, or composites thus produced serve as sourcematerial for subsequent extrusion processes.

All above-mentioned processing methods start with an intensivecompression of the feed material, which causes substantial heatgeneration due to the high pressure and intensive frictional forces. Inthe processing of thermoplastic synthetics, this causes a plasticizingof the feed material, and furthermore to the forming of granulates andagglomerates.

If at the input side, thermoplastic synthetics are mixed with additionalmaterials, for example, wood, the thermoplastic synthetics form a mushyto gooey matrix after plasticization, in which the further materials areembedded. The compounds thus produced then serve, as previouslydescribed, as source material for injection molding and extrusionapparatuses to produce construction and building materials of wood-likeappearance. To improve the quality of the compounds, additives, forexample, bonding agents, are frequently added to the feed material,which promote a wetting of the various components during theplasticization phase.

Quality problems with the product to be produced occur on a regularbasis when water is conveyed with the feed material to the compressionand processing zones. Due to the high temperatures prevalent there,water evaporates instantly and causes the formation of bubbles in theproduct to be produced. The resulting high pore volume contradicts theoriginal idea of maximum compacting. Furthermore, porous intermediateproducts have a high abrasion tendency, which makes their furtherprocessing in subsequent processing stages questionable or evenimpossible.

In order to avoid problems caused by the penetration of moisture orwater, it is known to dry each type of feed material in separatededicated drying devices prior to processing. The disadvantage of thisprocedure is the high cost resulting from maintaining suitable dryingdevices and the additional expenditure of keeping the operation running.

In connection with the agglomeration of scrap plastics, a method and anapparatus is known from DE 197 06 374, whereby the heat generated duringthe agglomeration process is utilized to evaporate the residual water inthe accumulated plastic scrap. By applying systematic loosening-upmeasures, the flow resistance on the input side is lowered such that thedeveloping steam escapes from the agglomerator away from the conveyingdirection of the feed material. By systematically channeling the steamto an injection condenser, a transition of the steam to a liquidaggregation state is made. The condensed matter is collected in thecondenser and is suctioned off with a pump.

Using this method and this apparatus, plastic scraps can be dried andagglomerated in one processing step. In connection with fine andfine-grained feed materials, however, it was found that steam escapingaway from the conveying direction picks up fine particles of the feedmaterial, which, apart from the loss of feed material, causes furthercomplications in the subsequent processing operation.

Another conventional method and corresponding apparatus is disclosed inDE 32 10 947 A1. In this device, the feed material is compressed in aconical screw press before it is finally forced through a slot or ringconstriction, where its highest compression is attained. During theinitial compression, water is mostly squeezed off in the area of thepressing screw. Developing steam escapes through a perforated pipesection that is attached to the pressing screw. After condensation, thesteam, together with the squeezed-off water, is removed.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide anapparatus and a method, wherein even fine and fine-grained feed materialthat is found in residual water can be processed into woodfuelbriquettes, pellets, compounds, composites, agglomerates, granulates,and the like, without lowering the quality of the product and withouthaving to suffer any loss of feed material.

The invention is based on the idea to vent the steam that is developingduring the processing of the feed material away from the conveyingdirection to prevent quality losses. However, fine and fine-grained feedmaterials pose the problem, that particles of the feed material arecarried away by the steam flow. The present invention makes it possibleto detach these particles from the steam flow and to return them to thefeed material. For this purpose, the steam flow is decelerated such thatthe lifting power of the steam flow is less than the effect of gravityon the particles. This allows the feed material that is carried away bythe steam flow to drop and to gather.

For this purpose, an apparatus of the present invention includes anexpansion chamber, which has a comparatively larger flow-through crosssection than the pressing screw. Initially, this causes the flow-throughresistance in this area to drop, which promotes a steam flow in thedirection of the expansion chamber. In addition, the comparativelyhigher flow-through cross section causes a deceleration of the flow,thus allowing the dropping of the floating feed material. The individualprocess parameters must be selected such that condensation of the steamdoes not occur in the expansion chamber because otherwise, the waterextracted from the feed material would get back into the feed material.In the course of successive cycles, more and more water wouldaccumulate, which ultimately would cause operational breakdowns.

In a beneficial embodiment of the invention, the expansion chamber isdesigned as part of the screw shell. This provides a short and directpath for the steam flow, which allows a direct dropping of thecarried-along particles onto the conveyor system of the apparatus.

Further preferred is an upstream, vertical flow through the expansionchamber, which is the most effective method of recovering the floatingparticles. The efficiency thus attained allows a space-saving, compactconstruction of an apparatus according to the present invention.

A closest-possible proximity of the expansion chamber to the processingtools results in minimizing the distance between the source of the steamand the area of escape so that the flow-through resistance of the steamis kept as low as possible. The short distance has the additional effectthat the steam flow has little opportunity to pick up feed material fromthe material conveyor.

In a further preferred apparatus, the side walls of the expansionchamber are essentially arranged vertically. This gives the floating ordropping particles little opportunity to settle and gather on horizontalor slanted surfaces. This measure contributes to a minimizing of themaintenance costs.

Preferably, at least one side wall of the expansion chamber can befolded up or detached to ensure access to the expansion chamber formaintenance or repair work. In addition, this type of constructionallows outside air to be channeled into the expansion chamber. The useof warm or hot air is thereby particularly beneficial because it worksagainst possible condensation.

Tests have shown that at a flow speed in the expansion chamber ofmaximal 5 meters per second, preferably at 3 meters per second, analmost total retrieval of the feed material from the steam flow ispossible. Although lower flow speeds improve the rate of deposition;however, they require larger expansion chambers. Higher flow speeds, onthe other hand, result in an increased quantity of feed material in thesteam flow after its exit from the expansion chamber, thus increasingthe loss of feed material.

In an embodiment of the invention, the steam passing through theexpansion chamber is channeled directly into the ambient air, whichcompletely absorbs the water contained in the steam. The special meritsof this embodiment are its simplicity in construction and operation,together with high operational safety.

In a further embodiment, the expansion chamber is attached to a lowpressure system. The low pressure thereby promotes the steam flow in thedirection of the expansion chamber. In a continuation of this idea, thesteam flow is channeled to a filter with the aid of the low pressure,where residual particles of the feed material, which are still presentin the steam flow, are separated and returned to the feed material. Forthis purpose, the filter is preferably connected to the feed chute via adownpipe.

Preferably, the low pressure is produced by a exhaust fan, which on itsintake side is connected to the filter. In order to prevent condensationof the steam in the expansion chamber, the low pressure lines, or thefilter, an adjustable air inlet is provided between the exhaust fan andthe filter, according to an embodiment of the present invention. Thisair inlet allows the systematic and adjustable entry of outside air intothe low pressure system, which also can be warm air, if need be. In thisway, the low pressure can be kept at a level that allows optimal flowspeeds to prevail in the expansion chamber.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, are not limitiveof the present invention, and wherein:

FIG. 1 is a longitudinal cross section of an embodiment of the presentinvention;

FIG. 2 is a longitudinal cross section of another embodiment of thepresent invention;

FIG. 3 is a front view of the apparatus illustrated in FIG. 2;

FIG. 4 is a longitudinal cross section of another embodiment of thepresent invention; and

FIG. 5 is a cross section along the line V-V of the apparatusillustrated in FIG. 4.

DETAILED DESCRIPTION

The embodiments illustrated in the drawings show an apparatus of thepresent invention in the form of an agglomerator without limiting theinvention thereto. The invention can as well be used in combination withan extruder, compactor or compressor, as described in DE 32 10 974 A1,for example, or with similar devices.

To begin with, an agglomeration apparatus is shown in FIG. 1, details ofwhich are known from DE 38 42 072 C1, which corresponds to U.S. Pat. No.5,009,586, and which is incorporated herein by reference. Essentially, acylindrical housing 1 that encloses the agglomerating zone, is shown.The housing 1 has a rear wall 2, the central area of which isconstructed as a horizontal housing bushing 3. The housing bushing 3serves as a horizontal rotatable mount for a drive shaft 4, which isonly partially shown, and which ends in a shaft journal 5.

Arranged on top of the shaft journal 5 is a rotor hub 6, from which twodiametrically opposed pressing blades 7 extend into a disk-shapedannular chamber 8. The annular chamber 8 is restricted by a rear annularwall 9, which is fixedly attached to the housing 1, and a front annularwall 10, which is part of a swing-out housing cover 11. In itsperiphery, the annular chamber 8 is enclosed by a perforated die 12,which, together with the effective edges of the rotating pressing blades7, is doing the actual agglomeration work.

The exterior of the perforated die 12 is swept by two rotating knives13, which are adjustably and exchangeably attached to knife holders 14.The knife holders 14 are arranged on a knife holder hub 15, which inturn is rotatably positioned at the outer periphery of the housingbushing 3.

Central to the housing cover 11 and jointly pivotable, a pressing screw17 is mounted as an extension of a rotational axis 16. The pressingscrew 17 has a screw shaft 18, which extends coaxially with therotational axis 16, with a single-turn screw spiral 19 rotating thereon.The screw spiral 19, in turn, is enclosed by a screw shell 20. At thefree end of the pressing screw 17, a vertical feeder chute 21 leads intothe screw shell 20, whereas at the opposite end, the screw dischargeextends into the annular chamber 8 of the agglomerator.

In the area between the feeder chute 21 and the housing cover 11, invery close proximity to the housing cover 11, is an expansion chamber23, which extends upwards in a substantially vertical direction inrelation to the rotational axis 16. The expansion chamber 23 is formedby an opening 24 in the screw cover 20, and is enclosed by vertical sidewalls 25. In the present embodiment, the expansion chamber has arectangular cross section, however, the cross section thereof can be anyshape, for example circular, elliptical, square, etc. The side walls,which are plane-parallel to the illustration plane, emerge tangentiallyfrom the screw shell 20, that is, the cross-section measurement of theexpansion chamber 23 transversal to the screw shaft 16 equals thediameter of the screw shell 20. The minimum height of the expansionchamber 23 depends on the sedimentation behavior of the feed material.It should be made certain that the individual particles are able to dropinside the expansion chamber 23.

The apparatus illustrated in FIG. 1 works as follows. The feed material,as indicated by arrows 26, is conveyed via the feeder chute 21 to thearea of the pressing screw 17, where it is pushed by the rotating screwspirals 19 into the disk-shaped annular chamber 8. The feed material canbe a mixture of, for example, saw dust and thermoplastic granulates.

The pressing blades 17 rotating in the annular chamber 8 compress thefeed material in the direction of the perforated die 12, which generatesa considerable amount of heat due to the friction forces in action. Thisresults in the plasticization of the thermoplastic part of the feedmaterial, which in turn causes at least a partial wetting of the sawdust by the plastic synthetic material. This mushy to gooey mixture ofsaw dust and thermoplastic synthetic material is subsequently pressedradially outward through the holes in the perforated die 12, whereby anintensive mixing and compressing takes place. The agglomerate 31, whichis thus formed on the outside of the perforated die 12, is cut off bythe rotating knives 13, and is subsequently removed via the materialoutput 27 at the bottom of the housing 1.

By conveying the feed material to the disk-shaped annular chamber 8, thechamber is heated up considerably due to the high temperatures generatedin the agglomeration process so that the water retained in the feedmaterial changes into a gaseous state of aggregation instantly, that is,it evaporates. The volume increase associated therewith generates steampressure, which due to the prevailing flow resistances causes the steamto flow in an opposite direction from the conveyor direction of thescrew spiral 19. In FIG. 1, the steam flow is referenced with thenumeral 28. The lowest flow-through resistance is in the area of theexpansion chamber 23 so that the steam flow 28 enters the expansionchamber 23, flows through it in a vertical direction, and escapes at itsupper end through an opening 29, and disperses into the ambient air.

Due to the high flow speed, the steam flow 28 picks up fine particlesfrom the feed material during its passage through the pressing screw 17so that they are carried by the steam flow 28 into the expansion chamber23. Owing to the larger flow-through cross section of the expansionchamber 23 as compared to the pressing screw 17, a systematicdeceleration of the steam flow 28 takes place such that the effect ofgravity on the particles of the feed material in the expansion chamber23 is stronger than the sweeping power of the steam flow 28. Thus, theparticles drop back into the pressing screw 17, where they are thenchanneled back into the agglomerating process by the screw spiral 19.

FIGS. 2 and 3 show a further embodiment of the apparatus described inFIG. 1. The agglomerator and the pressing screw are comparable to thosein FIG. 1 so that the same reference numerals are used for the samecomponents, and the description of FIG. 1 applies.

The additions illustrated in FIGS. 2 and 3 are essentially directed tothe expansion chamber 30, which has been combined with furthercomponents to the apparatus. In contrast to FIG. 1, the expansionchamber 30 illustrated in FIGS. 2 and 3 is closed on the top and has anexhaust pipe 32 in this area, the longitudinal axis of which is inclinedby the angle α against the vertical axis. Thus, the exhaust pipe 32leads into the expansion chamber 30 at an angle, and with its lower wallforms an inclined side wall of the expansion chamber 30. The maximalsize of the angle α has to be such that the feed material droppingthrough the exhaust pipe 32 does not settle and gather on the inclinedsurface, but slides downwards into the pressing screw 17.

A pipeline 33 of smaller diameter is connected to the exhaust pipe 32.The pipeline 33 ends in the housing of a filter 34. The filter housingis comprised of an upper cylindrical part 36 and a lower funnel-shapedfilter leg 37 attached thereto. The cylindrical part 36 serves as areceptacle for vertically arranged filter elements 38, 38′, which areillustrated in FIG. 2 only. FIG. 2 shows two different states ofoperation of the filter elements 38, 38′, which always occur atdifferent times. The filter element 38 illustrates the normal state ofoperation, whereby residual feed material is detached from the steamflow, whereas the filter element 38′ illustrates the backwashing of thefilter.

Above the filter 34, there is an exhaust fan 39, which is part of aprimary air system and which has the function to generate a low pressurein the filter 34. The effect of the low pressure extends via thepipeline 33 to the expansion chamber 30 and the pressing screw 17.Located between the filter 34 and the exhaust fan 39 is an adjustabledamper 41 to inject outside air, warmed up air, as the case may be, intothe primary air system.

At its lowest point, the funnel-shaped filter leg 34 has an outlet, towhich a downpipe 42 is attached. At its lower end, the downpipe 42 endsin the feeder chute 21 of the pressing screw 17 and can be closed with asealing element 46. The sealing element 46, for example, a slide damper,a butterfly valve, or a cell sluice valve, is closed during regularoperation and is only opened for backwashing the filter. To supply thepressing screw 17, a branch pipe 43, which is laterally arranged on thedownpipe 40, is provided for the intake of the feed material, as isindicated by the arrow 44.

The functions of the agglomerator and the pressing screw 17 are similarto those described in FIG. 1 so reference is made to this part of thedescription. Accordingly, the steam flow 28 escapes from theagglomerator in a direction opposite to the conveyor direction of thepressing screw 17, which is supported by the low pressure generated bythe exhaust fan 39. Due to the prevailing flow speed in the pressingscrew 17, particles of the feed material in the pressing screw 17 arepicked up by the steam flow 28 and carried to the expansion chamber 30.The larger flow-through cross section of the expansion chamber 30 causesa deceleration of the steam flow 28 with the result that most of theparticles drop and are returned to the agglomerator by the screw spiral19. However, a residue of fine and finest particles always remains inthe steam flow 28.

After its exit from the expansion chamber 30, these fine and finestparticles are carried by the steam flow 28 through the pipeline 33 tothe filter 34. In the filter 34, a final separation takes place, wherebythe particles are retained by the filter surfaces of the filter elements38, whereas the cleansed steam flow 28, after passing through the filterelements 38 and the exhaust fan 39, escapes into the ambient air.

After a period of operation, a decrease of the effective filter surfaceof the filter elements 38 can be observed, which can be noted in anincreased energy consumption of the exhaust fan 39 at constant lowpressure, or a decrease of the low pressure in the expansion chamber 30at constant exhaust fan operation. To clean the filter elements 38, theyare backwashed at appropriate time intervals. By activating thesecondary air system, compressed air from the compressed air duct 40 isthereby blown via the backwash lines 45 into the filter elements 38. Theforced reversal of the flow direction through the filter causes the fineand finest particles on the surface of the filter elements 38 todislodge and to drop into the funnel-shaped filter leg 37 by force ofgravity. With the sealing element 46 opened, they drop through thedownpipe 42 into the feeder chute 21 of the pressing screw 17, whichcloses the material cycle and completely retrieves the portion of thefeed material that was carried off by the steam flow 28.

FIGS. 4 and 5 illustrate a third embodiment of the invention.Agglomerator and pressing screw are thereby also identical to thosepreviously described so that once again identical reference numerals areused for identical parts, and reference is made to correspondingsections of the descriptions for FIGS. 1 to 3.

In the apparatus according to the present invention, as illustrated inFIGS. 4 and 5, the expansion chamber 50 is extended by a vertical duct51 with an identical cross section, and ends with its upper end in afilter 52. The filter 52 is essentially the same as described in FIGS. 2and 3, that is, the filter 52 includes filter elements 53, 53′, whichcan be backwashed via a compressed-air system 54. Again, FIG. 5illustrates two states of operation, namely, the normal filter operationwith the filter element 53, whereas the filter element 53′ illustratesthe backwashing of the filter.

On its upper side, the housing of filter 52 is connected to a lowpressure system, which is indicated by the arrow 55. As described inFIGS. 2 and 3, the low pressure system can include an exhaust fan, whichis arranged directly by the filter, or a primary central low pressuresource, which may also supply further components of other parts of theapparatus. In this embodiment, an intake of an outside air streamdownward to the filter 52 may be provided as well. The effect of the lowpressure extends via the duct 51 and the expansion chamber 50 all theway to the pressing screw 17.

The function of this embodiment of the invention is as follows. On itsway to the pressing screw 17, the steam flow 28 sweeps up fine particlesof the feed material and, supported by the low pressure, enters theexpansion chamber 50. Due to the larger flow-through cross section, adeceleration of the flow 28 takes place, which allows the particles fromthe feed material to drop in an direction opposite to that of the steamflow. As a result of the upward extension of the expansion chamber 50through the duct 51, there is more time and space for the feed materialthat is carried along by the steam flow 28 to detach itself from thesteam flow 28.

Finest particles, however, continue to be carried by the steam flow 28to the filter 52, where a final separation on the surface of the filterelements 53 takes place. In the course of the continuous flow 28 ofsteam through the filter elements 53, the moisture carried along in thesteam flow 28 causes a gradual soaking of the finest particles attachedto the filter elements 53. They form clumps, with the result that duringbackwashing of the filter elements 53′, larger clumps, which areindicated in FIGS. 4 and 5 with the reference numeral 56, detachthemselves from the surface of the filter elements 53. Due to theirweight, the clumps 56 drop in an opposite direction to the steam flow 28through the duct 51 and the expansion chamber 50 back into the pressingscrew 17, as is indicated by the arrows 57.

The invention being thus described, it will be obvious that the same maybe varied in many-ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are to beincluded within the scope of the following claims.

1. An apparatus for producing woodfuel briquettes, pellets, compounds,composites, agglomerates, or granulates, the apparatus comprising: apressing screw having screw spirals that rotate around a longitudinalaxis and that are arranged Inside a screw shell; a feeding chute forconveying feed material to the pressing screw, the feeding chute beinglocated at an input side; processing tools, which are arranged at an endof the pressing screw and to which the feed material is conveyed by therotating screw spirals; and an expansion chamber through which escapingsteam flow is channeled, the steam being generated in an area of theprocessing tools by residual moisture in the feed material due to heatbeing generated during the processing procedure, the expansion chamberhaving a flow-through cross section at a location of an opening of thescrew shell such that it causes the steam flow to decelerate and forallowing particulate matter contained in the escaping steam flow, whichescapes into the expansion chamber, to fall back from the expansionchamber into the screw shell.
 2. The apparatus according to claim 1,wherein the expansion chamber is formed as a portion of the screw shell.3. The apparatus according to claim 1, wherein the expansion chamber isarranged on the pressing screw in substantially a vertical flow-throughdirection.
 4. The apparatus according to claim 1, wherein the expansionchamber is arranged in a close proximity to the processing tools.
 5. Theapparatus according to claim 1, wherein side walls of the expansionchamber are substantially vertically arranged.
 6. The apparatusaccording to claim 1, wherein at least one side wall of the expansionchamber can be folded up or detached.
 7. The apparatus according toclaim 1, wherein, in the expansion chamber, a maximum flow speed of 5m/s is prevalent.
 8. The apparatus according to claim 1, wherein theexpansion chamber can be pressurized with low pressure.
 9. The apparatusaccording to claim 8, wherein the low pressure source is provideddownstream to the expansion chamber.
 10. The apparatus according toclaim 1, wherein, downstream from the expansion chamber, a filter isarranged to filter out feed material.
 11. The apparatus according toclaim 10, wherein, for the purpose of returning the feed material, thefilter is connected to the pressing screw, preferably to the feederchute.
 12. The apparatus according to claim 11, wherein a connectionbetween the filter and the pressing screw or the feeder chute can besealed by a sealing element.
 13. The apparatus according to claim 10,wherein an exhaust fan is arranged behind the filter in a flow-throughdirection to generate the low pressure.
 14. An apparatus for producingwoodfuel briquettes, pellets, compounds, composites, agglomerates, orgranulates, the apparatus comprising: a pressing screw having screwspirals that rotate around a longitudinal axis and that are arrangedinside a screw shell; a feeding chute for conveying feed material to thepressing screw, the feeding chute being located at an input side;processing tools, which are arranged at an end of the pressing screw andto which the feed material is conveyed by the rotating screw spirals;and an expansion chamber through which escaping steam flow is channeled,the steam being generated in an area of the processing tools by residualmoisture in the feed material due to heat being generated during theprocessing procedure, the expansion chamber having a flow-through crosssection such that it causes the steam flow to decelerate, wherein,downstream from the expansion chamber, a filter is arranged to filterout feed material, wherein an exhaust fan is arranged behind the filterin a flow-through direction to generate the low pressure, and wherein anadjustable air inlet is arranged between the exhaust fan and the filter.15. The apparatus according to claim 1, wherein the processing tools arean agglomerator.
 16. The apparatus according to claim 1, wherein theprocessing tools are an extruder.
 17. The apparatus according to claim1, wherein the processing tools are a compactor.
 18. The apparatusaccording to claim 1, wherein, in the expansion chamber, a maximum flowspeed of 3 m/s is prevalent.
 19. An apparatus comprising: a feed chutefor receiving feed material; processing tools for processing the feedmaterial; a screw shell for housing a screw, the screw providing thefeed material from the feed chute to the processing tools; and anexpansion chamber being provided on the screw shell and being locatedbetween the feed chute and the processing tools, the expansion chamberallowing steam, which is generated by the feed material being compacted,to dissipate from the screw shell, wherein a portion of the expansionchamber at a location of an opening of the screw shell is formed suchthat a flow amount of the dissipating steam is decreased so that feedmaterial that is carried into the expansion chamber by the dissipatingsteam is redirected towards the feed material.
 20. The apparatusaccording to claim 19, wherein the expansion chamber has a diameter thatis substantially equal to a diameter of the screw shell.
 21. Theapparatus according to claim 19, wherein the expansion chamber has adiameter that is greater than a diameter of the screw shell.
 22. Theapparatus according to claim 19, wherein the expansion chamber has adiameter that is less than a diameter of the screw shell.
 23. Theapparatus according to claim 1, wherein the flow-through cross sectionof the expansion chamber is substantially equal to a diameter of thescrew shell.
 24. The apparatus according to claim 1, wherein theflow-through cross section of the expansion chamber is greater than adiameter of the screw shell.
 25. The apparatus according to claim 1,wherein the flow-through cross section of the expansion chambertransverse to the longitudinal axis of the pressing screw issubstantially equal a diameter of the screw shell.
 26. The apparatusaccording to claim 1, wherein the expansion chamber includes sides wallsextending vertically from the opening of the screw shell, and whereinthe flow-through cross section of the expansion chamber is greater thana cross section of the screw shell.